unexpected bicycles and inattentional blindness

By Daniel Simons, on June 22nd, 2010

This article reports a tragic accident that happened on Sunday. A bicyclist was hit by a car and killed. Unfortunately, such accidents are far too common, and this particular example typifies how inattentional blindness operates in the real world.

Most people believe that unexpected or unusual events draw attention, perhaps even more than typical events. Why? In part, the belief is based on our experiences. When, on occasion, we happen to notice something unusual or unexpected, that event is remarkable. We take mental note of it and remember it. When we notice a typical or expected event, that’s unremarkable. Critically, we are, by definition, unaware of any events we don’t notice. If we fail to notice unexpected events more than expected ones, we won’t be aware of those probabilities. So, when intuitively judging how likely we are to notice events, we tend to think we notice unexpected ones more because htose are the ones we remember, and we lack the information to calculate the relative rates of noticing for expected and unexpected events.

As best we can tell from the existing data, people are more likely to notice events that are consistent with our expectations. For example, pedestrians and bicyclists are less likely to be hit by cars in towns where there are more pedestrians and bicyclists. We discuss this topic in The Invisible Gorilla, and Tom Vanderbilt covers it beautifully in his book Traffic.

So what happened in this case? A 42 year old bicyclist was riding down Highway 18 in the Town of Summit (in Wisconsin) when he was struck from behind by a 20 year old driver. According to the article, police are still investigating why the driver didn’t see the cyclist, but Officer Dana Hazelton noted that bicyclists rarely ride on the highway because “There’s actually a bicycle trail that’s just south of Highway 18 that’s probably 20 feet off the road that’s made for bicyclists.” In other words, people don’t expect to see bicyclists riding on the side of the highway, so they are less likely to notice them.

The same problem explains why drivers often fail to yield to motorcyclists when turning left — motorcycles are less common than cars, so drivers are less likely to see them, and occasionally look right at them without noticing.

Chest thump to Vicki McKenna for forwarding the link to the news story.